Methods and apparatus for aligning a communications frame to a predetermined phase

Abstract

Erroneous data due to faults are prevented from propagating through a distributed network node having diversely routed communications links by using a fault masking technique that eliminates the 60 ms of error propagation time associated with SONET networks. The fault masking technique can also prevent random bit errors from propagating through the distributed network node. A frame alignment technique used in the network node is scalable for very wide words (e.g., 128 bits) for use with high speed optical communications protocols, such as OC-192.

1. A method for aligning a frame of data in a network element to a predetermined phase, comprising:
 adjusting at a first granularity the phase of an out-of-phase frame of data in the network element to an intermediate phase, the first granularity being based on a first predetermined pattern of data in the frame of data, adjusting at the first granularity including shifting the data in the frame of data less than the length of the first predetermined pattern in the frame of data; and 
 adjusting at a second granularity the intermediate phase of the frame of data to align the frame of data to the predetermined phase, the second granularity being based on a second predetermined pattern of data in the frame of data, adjusting at the second granularity including shifting the data in the frame of data in increments equal to the length of the first predetermined pattern. 
 
     
     
       2. The method according to  claim 1  wherein the first predetermined pattern of data is related to the second predetermined pattern of data. 
     
     
       3. The method according to  claim 1  wherein the first granularity is finer than the second granularity. 
     
     
       4. The method according to  claim 1  used to align frames with interleaved data. 
     
     
       5. The method according to  claim 1  further including:
 determining a position location of the first predetermined pattern in the frame of data; and 
 determining a transition location from the first predetermined pattern to the second predetermined pattern. 
 
     
     
       6. The method according to  claim 5  wherein the predetermined patterns are related to the phase of the frame of data. 
     
     
       7. The method according to  claim 1  used in a Synchronous Optical Network (SONET) network or Synchronous Digital Hierarchy (SDH) network. 
     
     
       8. The method according to  claim 1  wherein shifting the data in the frame of data in increments equal to the length of the first predetermined pattern further includes shifting in increments in a range between one and a total number of pattern detectors comparing variations of the second predetermined pattern to data in the frame of data. 
     
     
       9. An apparatus for aligning a frame of data to a predetermined phase, comprising:
 a first aligner that adjusts with a first granularity the phase of an out-of-phase frame of data to an intermediate phase, the first granularity being based on a first predetermined pattern of data in the frame of data, the first aligner configured to adjust the frame of data less than the length of the first predetermined pattern in the frame of data; and 
 a second aligner that adjusts with a second granularity the intermediate phase of the frame of data to align the frame of data to the predetermined phase, the second granularity being based on a second predetermined pattern of data in the frame of data, the second aligner configured to adjust the frame of data in increments equal to the length of the first predetermined pattern in the frame of data. 
 
     
     
       10. The apparatus according to  claim 9  wherein the first predetermined pattern of data is related to the second predetermined pattern of data. 
     
     
       11. The apparatus according to  claim 9  wherein the first granularity is finer than the second granularity. 
     
     
       12. The apparatus according to  claim 9  used to align frames with interleaved data. 
     
     
       13. The apparatus according to  claim 9  wherein:
 the first aligner determines a position location of the first predetermined pattern in the frame of data; and 
 the second aligner determines a transition location from the first predetermined pattern to the second predetermined pattern. 
 
     
     
       14. The apparatus according to  claim 13  wherein the predetermined patterns are related to the phase of the frame of data. 
     
     
       15. The apparatus according to  claim 9  used in a Synchronous Optical Network (SONET) network or Synchronous Digital Hierarchy (SDH) network. 
     
     
       16. An apparatus for aligning a frame of data to a predetermined phase, comprising:
 means for adjusting at a first granularity the phase of an out-of-phase frame of data to an intermediate phase, the first granularity being based on a first predetermined pattern of data in the frame of data, the means for adjusting at the first granularity including means for shifting the data in the frame of data less than the length of the first predetermined pattern in the frame of data; and 
 means for adjusting at a second granularity the intermediate phase of the frame of data to align the frame of data to the predetermined phase, the second granularity being based on a second predetermined pattern of data in the frame of data, the means for adjusting at the second granularity including means for shifting the data in the frame of data in increments equal to the length of the first predetermined pattern.